The pacarana (pictured) is the closest living relative of the newly discovered fossil mammal Josephoartigasia monesi, announced as the world's largest known rodent on January 16, 2008.

While dwarfed by the extinct, bull-size J. monesi, the 33-pound (15-kilogram) pacarana is a giant by modern-day rodent standards.

The thick-tailed pacarana lives only in central South America, where the animal hides away in the forested foothills of the Andes mountains. A slow-moving, nocturnal plant-eater, the rodent is said to resemble a huge guinea pig or spineless porcupine.